Role and mechanism of action of p62/Sqstm1 in Ras-induced tumorigenesis in lung

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Project Summary/Abstract Lung cancer is the leading cancer-related cause of death in the United States. Current treatments do not lead to a cure for most patients with this type of neoplasia. Targeted anti-tumor therapies are likely to prove more effective, but their development will require a better understanding of the signaling cascades involved. Ras oncogenes are frequently mutated in human cancers where they play an unquestionably important role in the genesis and progression of the disease. In lung adenocarcinomas, mutations in Ras are present in at least 25% of cases, suggesting that the components of Ras-related signaling pathways are promising candidates for therapeutic targets in lung cancer treatment. Ras oncogenic transformation activates NF-¿B, a critical regulator of cell survival and an essential mediator of tumor progression. The atypical PKCs (aPKCs) and their adapter p62 are implicated in the control of NF-¿B activation. Recent results demonstrate that genetic inactivation of the NF-¿B pathway may either prevent or promote tumor development, depending on the target organ and whether or not the inflammatory response is involved. However, the effect of NF-¿B inactivation in lung neoplasia has not yet been documented. Preliminary studies demonstrate that Ras reproducibly produces lung adenomas and adenocarcinomas in an inducible model of lung cancer in mice, and that p62 is required for these Ras-induced lung tumors. The evidence suggests that this is a cell-autonomous effect in that the absence of p62 severely impairs the ability of Ras to transform immortal embryo fibroblasts. In addition, Ras transformation induces p62 protein accumulation through a yet-to-be-defined mechanism. These important observations strongly indicate that p62 is necessary for Ras-induced lung tumorigenesis and cell transformation. The long-term goal of this project is to define novel signaling molecules that could be therapeutic targets in lung cancer. The overall objective of this proposal is to rigorously test the hypothesis that the p62/aPKC/NF-¿B pathway is critical in Ras-induced tumor transformation, specifically in lung cancer. This will be achieved by assessing the roles and mechanism of action of these important signaling mediators in the regulation of Ras-induced transformation. The specific aims designed to achieve this are to 1) Test the hypothesis that p62 regulates Ras-induced lung cancer in vivo through the aPKCs; 2) Test the hypothesis that IKK¿ or IKK¿ are critical mediators of Ras-induced formation of lung tumors; 3) Elucidate the cellular and molecular mechanisms of the p62/aPKC/ NF-¿B pathway in Ras-induced transformation and its relevance in human lung cancer. This work will increase our understanding of the mechanisms involved in the regulation of lung cancer, and in the long term will provide the knowledge necessary for the development of novel, more specific, and thus less toxic, therapies for this type of neoplasia.